Auxiliary air heater



- May 3, 1949. 4 M. E. YEAGER ETAL 2,458,909

` AUXILIARY AIR HEATER I Filed Jan. 5, 1946 2 sheets-,sheet 1 NVENTORS May 3, 1949. M. E. YEAGER ETAL AUXILIARY AIR HEATER 2 Sheets-Sheet 2 Filed Jan. 3, 1946 1% INVENTORJ BY da@ j.' )W5 /f/WJ Patented May 3, 1949 AUXILIARY AIR HEATER Milburn E. Yeager, Needham, and Andrew J. Cnossen, Rehoboth, Mass.;y Evelyn M. Yeager executrix of said Milburn E. Yeager, deceased; said Evelyn M. Yeager assigner to said Cnossen Application January 3, 194.6, Serial No. 638,878

2 Claims.

The present invention relates to the heating art, and has particular reference to a novel auxiliary air heater which utilizes the heat in waste flue gases. f

The principal object of the invention is to provide an improved auxiliary air heater suitable for a domestic heating plant or the like.

An additional object of the invention is to provide an auxiliary air heater which may be readily installed to cooperate with an existing heating arrangement for providing additional heat from the waste flue gases.

yStill another object of the invention is to provide an auxiliary air heater which operates only when the temperature of the flue gases is sufiiciently7 high to provide effective heat transfer.

A further object of the invention is to provide an improved power driven air heater unit which forces cool air in heat transferring relation to hot ue gases which are ordinarily wasted in passing to the smoke stack.

With the above and other objects and advantageous-features in view, the invention lconsists of a novel arrangement of parts more fully disclosed in the detailed description following. in conjunction with the accompanying drawings, and more specifically dened in the appended claims.

In the drawings:

Fig. l is a perspective view showing an illustrative oil burner heating unit of the type ordinarily used for heating and similar installations, with which an auxiliary air heater embodying the present invention is'incorporated;

Fig. 2 is an enlarged vertical section through the auxiliary air heater, parts being broken away, showing the travel of cool air to be heated in heat transfer relation to the hot flue gases;

Fig. 3 is a perspective'view of the novel motor driven fan, showing the adjustable air in-take therefor; y

Fig. 4 is a perspective view of a modified. construction of flue gas heater suitable for larger installations;

Fig. 5 is a section on the line 5-5 of Fig. 4; and

Fig.' 6 is a perspective. skeleton View of Fig. 5 illustrating the paths of the air and the flue gases therethrough.

It has been found desirable to provide an auxiliary air heater for heating installations of the domestic type, which utilizes waste heat in the flue gases to provide heated air, whereby the heated air may be used to supplement the heating effect or to provide heated air for other uses, the additional heat absorbed from the flue gases being substantial in amount and the cost of operation only a small proportion of the savings vob'- tained. To this end, We have provided a simple construction of air heater which may be readily mounted on an existing smoke stack or flue pipe, and which has an electrically driven fan with a controlled air intake,the fan blowing cool air around and in close contact with the flue pipe so as to eliminate air lm and obtain a maximum heat transfer; the operation of the fan is preferably automatically controlled by an air temperature control or the like which is set to close the fan circuit when the temperature of the flue gases is sufficiently high to permit substantial heat transfer from the Waste flue gases. The heated air may be piped to any area which is hard to heat, and it has been found that the resulting air flow provides a quickr equalization andyuniformity of the heating effect.

Referring to the drawings, which illustrate a preferred embodiment of our invention suitable for small heating installations, the auxiliary air heater I0 is shown mounted on the flue gas pipe II of an oil burner system I2, the flue gases exiting to a chimney or smoke-stack I3. The auxiliary heater I0 includes an outer casing or shell I 4, 'illustrated as of rectangular section, which has end walls I5 and I6`provided with flanged openings I'I, I 8 to be mounted directly on the flue pipe I I, to form an enclosing casing. Mounted at one end of the auxiliary heater Ill is a fan casing I9 having a fan 20 which is electrically driven by means of an electric motor 2|, the fan having an open grill 22, s'ee Fig. 3, forming an air inlet. The open grill has a central outwardly projecting bolt 23 onrwhich a rotatable door 24 is threaded, to be manually turned by means of a handle 25 for controlling the amountV of air admitted to thekfan. I f y The lower end of the fan casing I9 is secured to the casing I4 and hasa flanged portion' 26 which has a centraloutlet 2'I and extends through a suitable opening 28 in the casing I4, whereby the fan can draw` air through the inlet grill 22 and discharge the air through the outlet 2l into the interior of the auxiliary -air heater I0 and around the ue pipe I'I. r A central baffle 26 is provided in the upper portion of the casing I4 so that the inowing air contacts the flue pipe I I downwardly and then upwardly in a tortuous path to pass into a heated air outlet pipe 29 mounted in an annular flange 30 secured to the upper surface of the casing I4, whereby the heated air can be conveyed to any point where additional heating is desirable.

Preferably, the speed of the fan is such that the incoming cool air flows over the surface of the flue pipe Il at such velocity that no air skin or air i'llm is formed on the flue pipe, and the maximum amount of heat is transferred from the flue gases to the heated air. As shown in Fig. 1, an air temperature control 3| is mounted in the side wall of the casing ld, to control the operation of the electric motor 2| by closing the circuit therefor, whereby the motor does not operate unless the ue gases are hot enough to provide an adequate auxiliary air heating. The control 3l is preferably set for a predetermined air heating temperature, for example 125? lit.,A and shuts the electric fan off whenever the air heatf ing temperature drops below the predetermined temperature.

The preferred auxiliary heater construction is illustrated in Figs. 1, 2 and 3, and provides suf-.fV cient heated air for a small installation. It has been. found desirable, for certain uses Where very hot airis required, to irierease the heat transf terrine Contact of the air with the het flue. eases in. order to absorb as much heat as possible- For such uses it is preferred to. utilize an auxiliary heater of the type shown in Fiss.k 4., and 6, in which the auxiliary air heater 32 is of cylindrical term, arid` includes a central pipe 33 in spaced concentric relation to the cylindrical outer surface, which pipe 3 3 is mounted between spaced portions 35 and 36 of the iiue pipe by means of brackets or straps 3 1, 38. The fan housing 39 provided with an @Een air inlet grill 4,0 and a disk member 4l forv regulating the amount of; air intake and the airinflow regulating disk member il is. threacliriely mounted. ori a bolt t2 aridhas an operating handle 43.l A fan similar to the fari 2u of. Fie. ,2., is mounted in the fan housing 39, and isl driven by an electric motor 44, the electric motor being controlled by; an` air temperature Control. 45, s irr1ilar to the control 3l Fie, 1,-

As shown in Figs. 5 and 6, a plurality of semicircular baijlles 40 are provided which are spaced apart as illustrated, whereby the Cool air from the fari easing is forced into the auxiliary air heater 32, and around the riotiiue. ses pipe S3 in atortuous helical path, to exity through an outlet pipe 41. which is preferably securedA to aridy madev integral with the upper surface of the auxiliary air heater 32, The pipe 33 is preferably provided with longitudinally disposed, central. metal fins 48 which4 quickly absorb, and transferheat to the outer shell of; the pipe for morev effective heat transfer from the hot flue gases toV the air to be heated. The longitudinal fin mounting does not restrict the flow of the nue gases, and facilitates cleaning and brushing of the flue pipe interior.

The Operation of the modified construction is like the operation of the construction shown in Figs. 1` to 3, except that the air to be heated traverses a longer path and therefore absorbs as much heat as possible from the hot flue gases, the fan being operated only when iiue gases are hot enough to provide adequate air heating.

We have found that the installation of the auxiliary heater absorbs a substantial percentage of the heat of the waste flue gases and provides a substantial amount of auxiliary heating, and compensates for unusual cold whenever the normal domestic heating installation lacks excess heating capacity. Further, we have found that the heated air may be piped to such places in a dwelling, factory or the like, as are normally diicult to heat, whereby the temperature within the dwelling or factory becomes equalized, with resulting lessening demand on the heating plant and a substantial saving in fuel,

Provision may be made, if desired, for the addition of water or other fluid to the air to be heated, so that the heated air does not become too dry.

Although the auxiliary air heater has been illustrated as applied to an oil fired domestic heating plant, it is obvious that the auxiliary air heater may be applied to the flue gas pipe of av coal red heater or to any other source of waste hot gases, thus providing an auxiliary heating unitv whichv has a very small cost of operation, and that the construction may be readily arranged as a system for cooling, by using the control pipe for a cold fluid and the outer casing for the flow of airv 1,50 be cooled.

We claim:

1. A heat exchanger comprising a cylindrical casi-ng, a central flue section having an axial opening at each end for connection in a flue, an air inlet opening in the casing wall adjacent one end, an air outlet opening in the casingl wall adjacent the otherv end spaced baffles of half torus shape mounted between said flue section and casing on opposite sides of the flue section, whereby air passingv through the casing to be heated alternately contacts,l opposite side portions of the ue section, and a thermostatically controlled blower device havingY its air outlet communicating with the exchanger inlet opening.

2. A heat exchanger comprising a cylindrical casing, a centrali flue section having anv axial opening at each end for connection in a flue, heat absorbing fins extending inwardly of said central flue section, an air inlet openingin the casing wall adjacent one end,l anair outletl opening in the casing wall adjacent the other end, spaced baiiies of half torus shape mounted between said flue section and casing on opposite sides of the flue section, whereby air passing through the casing to be heated alternately contacts opposite side portions of the flue section, and a thermostatically controlled blower device having its air outlet communicating withthe exchanger inlet opening.

M ILBURN E. YEAGER. ANDREW J. CNOSSEN.

REFERENCES CITED.

The following references are ofrecord in the file of this patent:

UNTED STATES: PATENTS Number Name Date 1,801,057 Samels. Apr. 14, 1931 2,362,940 Skerrittl Nov. 14, 1944 

